Electric percussion welding system



June 6, 1950 H. J. GRAHAM ELECTRIC PERCUSSION WELDING SYSTEM 4 Sheets-Sheet 1 Filed Sept. 28, 1946 MN N N M \%N k\ June 6, 1950 H. J. GRAHAM ELECTRIC PERCUSSION WELDING SYSTEM 4 Sheets-Sheet 2 Filed Sept. 28, 1946 June 6, 1950 H. J. GRAHAM 2,510,101

ELECTRIC PERCUSSION wzwms SYSTEM 4 Sheets-Sheet 3 Filed Sept. 2a, 1946 1 v If Jaye/ M0? flarraki 1 firnkmm PYW @J.

June 6, 1950 J. GRAHAM 2,510,101

ELECTRIC PERCUSSION WELDING SYSTEM Filed Sept. 28, 1946 4' Sheets-Sheet 4 2/9 JJFJ 250 r zip lllllllllllln VIIIIIIIIIII [77 0,2 7? far Patented June 6, 1950 ELECTRIC PERCUSSION WELDING SYSTEM Harold J. Graham, Boston, Mass., assignor, by mesne assignments, to Graham Manufacturing Corporation, Detroit, Mich., a corporation of Michigan Application September 28, 1946, Serial No. 700,136

17 Claims.

This invention relates to an electric welding and piercing system of the type wherein a mechanical impact tending to unite two construction elements is applied together with a current impulse.

One of the principal objects of the invention is to provide equipment of the above mentioned type whose impact applying component is normally disconnected from the source of electric welding energy and which depends for establishing an operative electric connection not upon the blow impact between its percussion elements, but separates the circuit preparing switching function from the blow or percussion function.

Other objects are to provide in equipment of this type for positive correlation of a loose work piece and a stationary work piece or tool element without direct contact; to provide a tool which is suited not only for welding but also for piercing; to provide a tool which is especially suited for welding studs to a stationary work piece; to provide a tool which is particularly suited for welding studs to flat surfaces, and to provide studs shaped to promote such welding; to provide such a tool which is for its current supply independent of internal contact making devices; to provide a percussion welding tool that can be easily adapted for operation with a welding circuit closed by a contact maker within the tool, or by a contact maker separated therefrom and associated with an automatic control circuit; to provide a welding system including a percussion welding tool and a circuit particularly suited, according to the invention, for operation with tools of that type; to provide welding equipment which incorporates a tool with normally restrained impact means imparting a blow to initially separated pieces to be joined with the welding current flowing therethrough immediately upon contact of the pieces, and which automatically prohibits operation if the pieces should initially come into accidental contact; to provide a welding tool of this type which permits regulation of the time relation between blow and closing of the welding circuit; and generally to provide percussion welding and piercing equipment which is simple, safe, inexpensive, easily serviceable, and yet reliable and adaptable fully to comply with the requirements of a wide variet of applications.

In one aspect, the tool according to the invention accomplishes these objects by means of two relatively sliding members which are connected by an energy supplying element as for example a spring, and one of which carries a hammer or plunger which is normally attached to its slide but released therefrom upon movement of the slides towards each other, the hammer carrying slide also carrying a force transmitting and contact making sliding element, so that the hammer or plunger, when released from its slide, first makes contact with and then applies a percussion blow to the transmitting element.

In another aspect, one of the slide members is provided with a distancer which permits applie cation of the tool by supporting it against one of the work pieces to be joined, such as a stationary piece, while releasing the percussion and contact making elements and performing the welding or piercing operation by pressing the other slide member towards the fixed work piece; in still another aspect, the invention provides for a piercing operation, by using in the above characterized welder, supplied from a suitable circuit according to the invention, a tool which has a tip of non-welding material for example tungsten and which, instead of being joined to a work piece, maintains an arc and penetrates that work piece, whereupon the piercing tool can be withdrawn, the are having been extinguished through collapse of the charge of a capacitor in the supply circuit, or opening of the circuit by switch means provided for that purpose; in a further aspect, the invention permits current supply directly to the tool holder by leading a conductor laterally through one of the slides; and in still another aspect, the new welder promotes proper circuit making and breaking by means of contact timing arrangements especially suitable for present purposes. Additional aspects of the invention are welding installations as a whole including tools according to the invention in combination with safety switch means that normally disconnect the tool from its supply circuit which may contain energy storing means such as capacitor means and connect it at the will of the operator whereupon the tool is ready for the automatic closing of contacts in series with the safety switch; installations with tools according to the, invention which have the above mentioned contact maker separate from the tool, in combination with a circuit which automatically prepares the welding circuit by means of a voltage responsive element when the required energy is available, closes it for the welding operation proper through the work pieces, and automatically opens the welding circuit by way of a switch element responsive to the welding current surge; and any installation which precludes welding and protects equipment and operator if the pieces to be 3 joined should make contact prior to the desired percussion impact.

Further features of the invention are a chuck particularly suited for welding disk studs to a fixed work piece; studs of peculiar shape particularly adapted for work with the Welding tool and welding equipment as a. whole according to the invention;' adjustable triggering means for releasing the hammer portion of the tool; and pneumatic means of the nature of a dash pot for adjusting the impact force dealt by the hammer element of the percussion welding toola'ccording' to the present invention.

These and other objects, aspects and features" will appear from the following description of two" typical practical embodiments illustrating the novel characteristics of my invention. This description refers to drawings inwhi'ch- Fig. 1 is a longitudinal section through a welding tool according to the invention;

Fig. 2 a section onlines 2-2 ofFig. 1; Fig. 31is 'a' section on lines 3"3 of Fig. 1; 4' i'sfjan elevation of a piercing tool which used with the equipment" according to Figs.

e. t i, v l M g. 5 is a jroiit' e eventh of a second embodiins-avenue invention; r v, I I

Fig, is a"section on lines 65-15 of Fig. 5

Fig.- '7 its: an elevation of a stud inserted in its wnicn i sh wn in sect on, which stud is p 6 ularly'suited for use with thetobl accordifigito Figsz5 ands:

M Fig-. 8 is anisoinetric view of a wedge shaped stiid tip suitablefor use with weldingtoo1saiii'dir'ig to the avenues: V I

fFigf 9 is a longitiidir'ial section are cussed stun t riff P Figi." 10fis' a fragmentary" section deiiffed from Fig. 6, o modified haihriier portion without ci'r'- edit closer Figs. 11 and lz'areaiag ramsof welding equip= meritincor oratingtools'accordingto'Figs; 1 to 7;

Fig. 13" is adiagram' of welding equipment in corporating a'tool adcor'ding to "Fig. 10-; and- Fig; 14 is a diagram of welding equipment in corporating a; tool of the type of- Fig. 6'with some modifications; this tool being shown in a 1ongitudinalsectionsimilar to'Fig; 6.-

InFigsa 1-; 2 and 3;-numeral Iii designates an outer guard and guide casing orhousing prefer-'- ably made from metal and'carrying, for example screwed thereto at I l,-a handle l zwhich may have any shape which is convenient for holding the tool against a work piece in the manner to be described hereinbelow;

-A-plunger casing 15, made from insulating material and having a groove I6 is slidingly fitted intothe guide casing In; a key I! of easing Ii] fits groove l6,- securing housings If] and I5 against other than straight line movement. a .Also secured to the housing ID, in the present instance forexample by means' of the above mentioned screw l I, is a releasing block 2! of insulatingmaterial, for instanceBakelite tubing. The blq'ck 2| has an extension 22 with an inside latch relieving bevel rim 23. Held between the releasingblock 2| and a spacer tube 24, likewise of insnlating material, is a terminal block 25 made of nietal and having abore of two diameters, as indicated at 3I and 32. The outer, larger bore 32 containsan insulating tube 33 whose inner diameter isthat of the inner bore 3|. End bore 3| and tube- 33 hold a metallic terminal cup 35, which ha s the purpose of receiving a conductor (not shown in the drawing) secured thereto by 4 means of a contact set screw 38. The tube 33 is held in block 25 by means of a set screw 39.

The terminal block 25 also has a central hole M for one end of a tail wire conductor 42 held therein by means of an appropriate set screw. The reduced head d6 of block 25 is provided with a thread 41 for holding the spring to be described hereinbelow.

Within the plunger casing l5 slides a plunger 5i with an impact and switch portion 52, and a core portion 53. A terminal block 55 fits the core portion 53 wherein it is held by means of set screws 58. The outer, larger portion of terminal block 55"is provided With a thread 5i, which is similar to, amines the same purpose as thread 41 of head at of block 25. Block 55 is further provided with a terminal bore GI and a conductor holding screw" similar to the corresponding elements of block 25.

A resetting spring 'H is inserted between the inside of easing l0 and the outside ofthe tubular front 'loitiif'fi'df block 2|; and between the shoulder 27' 6f blo'ck' 2i and the end faceof plunger casing i5. This spring is slightly compressed when the tool is in inoperative position as shown in Fig. l. I v p An" impact spring 72 is fastened to blocks 25 and 55' through engagement by threads 4 and 57; this spring is substantially untensibned' in normal condition of the tool, but becomes tensioned" during the operation and then becomes again slack.

The plunger 5| is related to plunger casingn5 by means of a latch device whih consists o'f'a' number, for example three spring latches (see also Fig. 3) whichnormally engage an insettt of casin'gf i5. Thelatch springs 85 are fastened to the plunger 5 by suitable means, for example rivets 83 (Fig; 1). The inclined cam faces 89 of springs 85 areso arranged that they are engaged by bevels 23 of tube extension 22, when the guide housing It] is pressed forward; so that upon contact with bevel 23, the springs 85 are moved inwardly; relieving plunger 5| from its casing l5 and constituting a timer which controls the interval between the electrical contact at 92 and the mechanical impact at I I9.

The above mentioned impact and switch por= tion 52 of plunger 5| has a face 9i surrounded by switch springs 92* which may be formed by applying saw cuts to a tubular projection of plunger 5|, as clearly indicated in Fig. 2;

Member ID! has a conical contact portion I06 which corresponds" to* contact springs 52. These two parts are so dimensioned and arranged that under normal conditions they are wholly sepa rated, whereas upon plunger 5! being released by retraction of latches t5; springs 52" engage cone H15 before the face I I9 of hammer IH en gages face 9'] of plunger 5],

A flexible conductor 42 is connected, within springs 12 to the above mentined contact d vices 4| and 6|. V

The forwarde'rld' of plunger; casing l5 carries screwed thereto, a cap ml which is extended into a chuck tube I02. The plunger casing l5 itself ends in a chuck casing portion 33 inside of chuck tube I02 and insulating the latter from a hammer sleeve H35 which carries a contact and these parts. A spring I09 tends to contact the chuck H5 with face II3 of sleeve member I05.

Base H5 is extended into a split chuck portion I2I which is threaded for a chuck sleeve I22, this arrangement permitting engagement, in the customary manner, of a Work piece w.

The chuck base as Well as the chuck sleeve are provided with insulating covers I25, I26 which, together with the above mentioned tubular extension IDS of plunger casing I5, fully insulate the hammer and chuck portions from cap IIlI and the distancing piece fastened thereto as now to be described.

The cap Ifil carries two or more distancer columns l3i, to which is fastened a distancer ring I32 which has a central opening I33 permitting penetration therethrough of the work piece 10.

The above described tool is used and operates in the following manner.

A work piece is, for example a pointed or edged stud, is inserted in the chuck I2I by tightening sleeve I22. The tool is then held against the work piece to which the stud w is to be joined by welding, with plate 132 resting against the flat work piece, with opening I33 marking the point to which w is to be joined. It is assumed that terminal 35 is connected to an appropriate source of current such as will be described hereinbelow and that the work piece to which is to be joined (which will be referred to as the large piece) is grounded or otherwise included in the welding circuit.

With distancer I3I, I32 held against the large work piece, pressure is now applied to end cap or handle [2. thus compressing springs II and 2 and causing tube IE] to slide forward on the stationary plunger casing :5. When bevel 23 reaches latch faces 69, the latches are moved inwardly and release plunger 5| from casing I5. Spring 12 thereupon drives plunger 5I rapidly towards hammer II I, establishing electrical contact at cone I35 and spring members 92, and shortly afterwards contacting the face II9 of hammer III. The hammer III is now advanced, against the force of spring I89 until the stud w is forcibly driven into contact with the large work piece. The hammer and hence the chuck I2I and the stud w being connected in the welding circuit through contacts 92IU6, the tip of work piece in strikes an arc while being forcibly contacted with the other work piece; a very strong joint is thus formed, due to the simultaneous application of welding current and percussion.

It will be understood that the welding current path must be continuous which, as above mentioned, can be accomplished by grounding the large work piece W to which the stud w is to be Welded, and by also grounding one side of the source of welding current, the other pole of which is connected to block and through the tail wire 42 to plunger 5I, hammer II2, chuck I2 I, and work piece in as shown in Fig. 11 which will be explained in detail below.

When the operator releases his pressure on handle :2, spring ll separates tubes I8 and I5 while returning into normal condition, and block 5! is quickly retracted by spring 12 which became compressed prior to the impact. Spring I2 pulls the plunger 55 with it until latches 85 engage the lining 85 of plunger casing I5. The chuck can now be opened and the tool withdrawn from the work piece in, whereupon the hammer III is returned into normal position by spring I09. The tool is now ready for insertion of another stud w and the next welding operation.

The above described tool is also very well suited for piercing of work pieces, especially sheets, in the following manner:

Instead of inserting a welding stud in into the chuck, a piercing rod such as shown in Fig. 4 is used, which consists preferably of a steel shank [95, if desirable but not necessarily tipped with non-welding material, such as tungsten, as indicated at I9I.

It was found in actual practice, that the are formed between the tungsten tip and the large work piece against which distancer I32 rests do not weld together if the accompanying conditions, particularly the speed of the blow are properly selected, but that the arc remains ef-' fective until the material has melted through the entire thickness of the work piece, whereupon the piercing rod is withdrawn.

Another embodiment of the invention will now be described with reference to Figs. 5, 6 and '7.

In Figs. 5 and 6, 2I2 is a cap which is screwed to a metal tube 2 i ii constituting a housing which holds against the cap 2I2 a block 222 and a disk 224 of insulating material which in turn hold a metal tube 226 having a. spring thread 221. Within tube 2H! slides another metallic tube or plunger casing 225, which is lined with a tube 2I6 of insulating material which has at its lower end a recessed portion 2 Il. This narrower portion has an inner rim 2 I8 against which rests a metallic tube m which is fastened to tubes 2It and 2H; by means of a bolt 226 with appropriate nuts HI and an insulating washer 222, which bolt rigidly connects the tubes 2 I 3, 2 I6 and 2H and also serves as an electrical conductor connecting tube 2H3 with a flexible wire introduced through a protective housing 233 attached to plunger casing 2 i 5 and having a grummet opening 23! with cover 232 (Fig. 5).

Pressed into tube 2It and abutting against metal tube 2IS is a hammer carrying tube 235 of insulating material which holds a metal sleeve 238 with a flange 23?. Within sleeve 23B is slidingly inserted a percussion block 240 having a contact and impact head 2M, a shoulder portion 2&2 and a chuck shoulder portion 243. For example by means of a sunk rivet 2 14 the chuck shank 2&5 holds a chuck 253 against shoulder 2 33. The chuck, also shown in Fig. 7, consists of a cup disk 25! which has an annular rim 252 provided with saw cuts 253, and a plate 254. This chuck is especially appropriate for holding a disk stud of the type shown in Fig. 7, which consists of a stud portion proper 2'63 fastened to a disk portion 253i. This disk portion is held in the chuck simply by inserting it into rin portion 252, slightly expanding the yielding saw cut portions which thereupon hold disk 26I pressed against the chuck plate 25-2'.

The tube 2I6 is confined within plunger housing tube 2l5 by means of a cap 2!! which has an opening 2H3 and may be provided with spacers 265. A spring 21% retains the chuck within the tube 2H3 by pressing chuck base 25I against sleeve 23%, as shown in Fig. 6, above mentioned opening M3 in cap 2i! being large enough to permit exit of the chuck from within tube 2E6.

Within metal tube 2H1 slides a plunger 280 which has a core portion 28I, and several latch springs 2B2, which in normal position lock the plunger against the inwardly protruding edge of inetal tube 2| 9. .I-Ield against the core 281i is a hammer piece 285, by means of a nut 285 whic'- is on the outside provided with a. spring thread 281. By means of the corresponding thread 221, a spring 2'i2 is fastened between plunger 285 and metal tube 228. Another spring 2?! is inserted between blocks 222 and 215, normally slightly tending to move tubes 2% and 2 it apart, against the tension of spring 212, thus retaining these housing members in the relative position shown in Fig. 6.

Hammer portion 285 holds, against core 28l, a contact spring cup 296 which has a tubular portion separated into spring elements 29l by means of saw cuts, as indicated in Fig. 6. Contact head 24! of block 248 is dimensioned to fit within the springs 29!, for making electrical contact therewith.

This welding tool operates as follows:

Contact stud 220 and therefore tubes 219 and 280 are connected to an appropriate current supply source, the stationary work piece is connected, and a disk stud is inserted in chuck 256. Spacers 265 are then pressed against the large stationary or otherwise fixed work piece to which stud 260 is to be welded. The spacers 265 are somewhat longer than the stud so that the latter is slightly distanced from the workpiece. Pressure is then applied against cap 2E2 which may be provided with a handle, until the inner edge of block 222 force's latch springs 282 inwardly, thereby releasing slide 21% which is then forcibly moved towards block 2%. Head 244 first makes contact with springs 2M, and shortly afterwards hammer 2E5 impacts head 24!, forcing the stud 260 towards the piece to which it is to be welded with the chuck emerging slightly from cap Zll, against the pressure of spring 210.

The welding takes place as above described, and upon release of pressure against cap 212, the springs withdraw plunger 28iI--28l until latches 282 again engage sleeve 259. Spring 279 thereupon withdraws hammer member 2 33, disengaging the chuck rim 25! from the stud disk 26!. The welding tool is thereupon ready for insertion of another stud and the next welding operation.

It will be noted that the embodiment according to Figs. and 6 avoids the necessity of having a flexible conductor between the connecting contact and the percussion elements of the tool, continuous contact being in this instance provided through sleeves 2l9 and 288.

Tools of this type can be used in the above mentioned supply circuits which will be described more in detail below, a tool according to Figs. 5 and 6 being shown in circuit diagram Fig. 12.

' It is understood that any convenient work holding device, chuck, or other similar appliance can be used with welding tools according to the present invention. Also, the spacers can be modified to suit any purpose at hand, and made exchangeable in accordance with the studs to be used. I

I found that for many purposes, particularly also for welding aluminum work pieces, pointed or edged tips are preferable to blunt tips. Simple points such as shown in Figs. 1 and 7 are often sufiicient, but particularly satisfactory results are obtained when the contact area is enlarged such as by extending the essentially point shaped tip according to Figs; 1 and '7 into a linear edge as shown at 3E9! of Fig. 8, or by extending it still further in the shape of a cupped tip with circular edge as shown at 302 of Fig. 9. The

8 larger contact area of tips according toFig. 3 and particularly Fig. 9 reduces the current density at the weld which is sometimes advantageous since certain metal sheets, for example of copper, tend to burn through instead of welding if the contact area is too small.

It is sometimes desirable under given working conditions to avoid electric contacts within the welding tool. In order to avoid such contacts, the present invention permits modification of Fig. 6 as shown in Fig. 10, this modification being suited for use in circuits of the type shown in Fig. 13.

Fig. 10 is similar to Fig. 6, with the following exceptions. The contacts 29! surrounding member 285 of Fig. 6' are omitted, the tool according to Fig. 10 having an impact member 385 which rests directly on slide member 280. The insulating sleeve 235 of Fig. 6 is replaced by a conducting sleeve 335 into which is screwed terminal stud 220, and which is separated from metal sleeve 2| 9 by an insulating tube SIG. It will be evident that welding current reaches the hammer member 243 directly through stud 220. sleeve 335, and spring casing 236 within which plunger 2&3 slides. Although this precaution is in most instances unnecessary, a flexible conductor 359 may be provided between sleeve 335 and plunger face 2 2 as indicated in Fig. 10.

The mechanical operation of the tool according to Fig. 10 is exactly as described above with reference to Figs. 5 and 6. The electric operation will be described below with reference to Fig. 13.

Circuits for use in systems incorporating tools of the above described type will now be described with reference to Figs. 11, 12 and 13.

Fig. 11 shows at d, c a current supply system which feeds into the welding network with limiting resistor Rand energy storing element C. which may be a conventional capacitor, an electrolytic cell, or any device able to accumulate energy for sudden discharge through the welding tool. Thus, the current supply with resistor and capacitor may be replaced by a storage battery of suitable energy content, or by a constant potential generator. One terminal of the capacitor C is connected to one work piece, in the present instance it is connected through ground g to sheet W. The other capacitor terminal is connected to tool terminal 31 and flexible conductor 2 as indicated in Fig. 1 as well as Fig. 11.

Capacitor C discharges through the circuit finally closed through work pieces wW, after this circuit has been prepared through closure at 92 and 1&1, shortly prior tothe percussion impact at 9! and H9.

The circuit according to Fig. 12 includes a tool according to Fig. 6 and has, in series with the internal welding switch 2i-2 ii, a safety switch sl, operated by a solenoid M i which is energized through a pushbutton or similar switch 82 preferably arranged on the welding tool or at the end of a flexible double conductor which at its end carries the switch ready for actuation by the welding tool operator. One contact of switch 82 is connected to ground, supply circuit, and stationary welding piece W, whereas the other contact of switch 82 is connected, through solenoid Ml, to the other terminal of the source. This source is in the present instance indicated as a battery B, which may be connected to an alternating current supply circuit, a, 0 through a rectifying and battery charging network No. One terminal of solenoid operated switch si is 0011- asidioi nected to the last mentioned source terminal, and the other contact of 5! is connected through flexible wire 280 to terminal stud 228 of the tool according to Fig. 6, which terminal is conductively connected to sleeve 2 I 9, as indicated also in Fig. 12. It will be understood that the flexible conductor 23$ leads through opening 23! of handle 230, shown in Fig. 6.

The equipment according to Fig. 12 operates as follows:

Switch s2 is normally open and only closed when the welding tool is in place with stud w distanced from sheet W and internal switch 2 ll- 25 open, that is before handle 21a is pressed towards stationary work piece W. When the operator is ready to exert pressure upon 210, he closes switch .92, energizing solenoid MI and closing switch s! which prepares the welding circuit. Pressure on 2!!! thereupon releases member (Fig. 6) and closes switch 241-29! with ensuing percussion welding as described above. After the weld is completed, switch 52 is again released which causes opening of switch sl after the welding circuit has been broken at 24 |29 l. The circuit is now again ready for operation. This arrangement avoids accidents, keeping the welding tool separated from the live supply terminal until it is ready for operation.

The equipment shown in Fig. 13 incorporates a welding tool without internal contact, as described above with reference to Fig. 10.

The internal contact maker is in this instance replaced by an external switch S, associated with and operated by solenoids M2 and M3 as follows. Contacts Mil, 402 of switch S are normally open, but closed when voltage solenoid M2 is energized, whereupon contact 402 is retained in closed position by latch Z, provided that solenoid M3 is deenergized, with w and W separated. Energization of solenoid M3 retracts latch l, releasing contact 402 and opening switch S. Contact 422 is connected, through solenoid M3, to terminal stud 220 of the welding tool according to Fig. 10. Solenoid M2 is connected between the two capacitor terminals, one of which is grounded and connected to the stationary welding piece, at g.

The arrangement according to Fig. 13 operates as follows:

When condenser C has attained its proper charge, determined for the purpose at hand, solenoid M2 closes switch S which is thereupon locked by latch Z. The welding circuit is now fully prepared and the weld is made when stud w touches work piec W after hammer 385 is released from, its holding latches 282 (Fig. 6). The welding current surge energizes solenoid M3 which attracts latch Z, permitting switch S to open. The capacitor C thereupon charges again and, upon the proper charge of C having been reached, the tool is again ready for operation.

Since the proper functioning f welding equipment according to the present invention depends upon initial separation of the two work pieces, it is important to make sure that this separation is actually present and to prevent initiation of the welding operation proper if the work piece which is to receive the percussion blow should accidentally contact the other work piece before that blow is rendered, simultaneously with supplying electric welding energy. The equipment now to be described with reference to Fig. 14 is suitable for that purpose.

The tool shown in Fig. 14 is in its principal elements quite similar to the embodiment described. with reference to Figs. and 6, as indicated by 10 the identical numerals used in both figures. The welding current is again supplied through a conductor 280 to a terminal stud 220 which feeds into sleeve 2 l 9 which, as in Fig. 6, is in current carrying connection with spring switch member 29l arranged for making contact with head 24] prior to the forcible contact or hammer 2325 and spring head 2 The insulating sleeve 235 is in the present instance provided with an auxiliary spring contact which, with head 2:36] and work holder 450 in normal, retracted position, makes contact with the head or screw 43%; insulated by sleeve 33'1 and screwed into terminal stud 438. A conductor 439 leads from terminal 433 to terminal l ll of the supply circuit.

Since the speed at which hammer 285 reaches head 2 may be essential for proper operation, an arrangement for regulating that speed is provided as follows. Tube is provided with hole c lia which has at its outer end a somewhat widened threaded portion 445 leading with a conical valve seat into the narrower bore 345. Screwed into the threaded portion 4% is a slotted adjusting screw W8 which, in well known manner, permits regulation of the air flow from the compression chamber defined by sleeve 2H3, piston like member 28! and insulator tube 235. Adjustment of the discharge port of hole M5 by means of screw l -i8 regulates the flow of air from. the above mentioned chamber and with it the advancing speed of hammer 285.

Fig. is also shows a provision for adjusting the relation of handle member 2lai-2i2 to the latch members 282 which, as described above, are released upon contact with edge 223 (Fig. 6) of sleeve 222 of the handle member 2E2. In Fig. 14, the length of member 222 is adjustable by means of unlatching sleeve 423 which is at 42% screwed into handle sleeve 222.

The circuit portion of the equipment according to Fig. 14 is shown as being supplied from a standard alternating current network a, c which feeds into transformers Ti and T2, supplying the anodes al a2 and the cathode is of tube V of the high vacuum, full wave rectifying type. This rectifier system feeds into direct current supply line 11, 0 one of these wires, for instance d, being connected at g to the stationary work piece W, and grounded. The other direct current terminal 0 is connected, through a limiting resistor Rl, to the terminal it of the welding tool.

One supply wire of the primary Tp of transformer Tl contains two switch contacts 45!, 452 which are normally connected by the movable contact member 453 of a control switch Si which is actuated by two solenoids Me and M5. Solenoid Mt is shunted by a timing capacitor C4 and connected in series with a timing resistor R5 connected to a tap it of a voltage dividing resistor R5, which has the purpose of supplying a reduced voltage to solenoid M4. A discharge resistor 1% is connected between direct current supply wires d, 0 through two contacts at! and 4552 which are normally open but are connected by switch member 453 if solenoid M4 is energized. A normally de-energized solenoid M5 is connected to the main supply wires a, 0 through a normally open pushbutton control switch S2.

Under normal conditions, both solenoids M4 and M5 are de-energized. Contact 453 closes the connection of transformer Tp to the source and is retained in that position by locking stop I) which, after M4 has been energized and with M5 de-energized, retains contact member 453 in ii ithfi unner position establishin c nn ct on hetween contacts at! and If .thereuog .noidIi ili is energized, locking member I) is l and, if is still de ener ized, contact is allowed .to disconnect lid ili52 and to reconne .4.5l.:l52.

The main welding condenser ,C is connected between direct current supply wires (2, ,c.

The equipment according to Fig. it operates .as follows:

Under normal operation, with stud w distanced from work piece W, solenoid M4 is ole-energized, contacts liii.l52.are connected, tube V is energized through transformer Ti, and contacts 435 l- .452 are disconnected.

The rectifier circuit including transformers Ti', T2, and tube V charges .the main capacitor C which discharges, .upon operation of the tool as abovedescrihed, .through terminal Alli lead 2%, terminal sleeve 2E9, contacts. 25 1-24-5, work holderciifi', and the work pieces in, W, which are now forced together by the spring action de scribed above with reference to Figs. .1 and If stud 10 should accidentally touch plate IN, a circuit is established irom resistor R representing avoltage source, through resistor R solenoid .Md .terminal dli-conduotor til-contacts 535, A35chuckil5il.plate .Wgro ..ind g back to resistor R5. Energization of solenoid M4 attracts the armature of switch contact A53, opening -the supply circuit of transformer nri mary T72 and thus de-energizing the rectifier tube V. Contacts Mil, 452 are now closed and .condenser C discharges through these contacts and resistor B6. In this manner discharge of the main capacitor through the welding tool is-safely avoided damage prevented.

The circuit can be reset to normal condition, after Md is de-energ-ized through disconnection between and W, with the armature portion 453 of switch Si resting against the locking latch b, by energizing solenoid through depressing switch S2which energizes solenoid M5 lifts b and releasescontact 853 which thereupon re-establishes connection between 45! and 452.

Thede-energization of M can be adiusted by means of capacitor C4 and resistor at whose time constant determines the rate of discharge of C4 and hence the period during which M remains effective. The speed at which Md becomes deenergized. and cuts off the rectifier tube supply and causes discharge of capacitor C through re siStOr R before any harm is done to the internal. circuit maker of the tool at Edi-49E. can thus be regulated. It will be apparent that adjustment of this period of time will. de end u on the possibility of handle 2M. being again depressed after the stud w has been detached the plate W, to a certain extent on the time elapsing be ween. the release or" latches and actual contact at 24! ?9l. This. d cussed above, can regulated by means of the delay valve 7MB, an arrangement of eifect.

It should be understood that the present disclosure is for the purpose illustration only and that this invention. includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. Electric welding apparatus comprising direct current supply means, capacitor means adapted to be charged from said supply means, normally closed switch means which upon opening render said supply means inefiective, means for positioning two work pieces to be joined relatively to each other in place for welding but with. one piece held at a distance from the'other normally preventing direct contact ltherebetween, impact means for releasing said piece and for forcing said pieces into mechanical contact, conductor means for electrically connecting'said pieces. to respective terminals of said capacitor means, energy consuming means connected in parallel to said capacitor means for discharge through a normally open switch means, relay means for retaining said switch means in normal positions when de-energized but upon energization opening said first switch means and closing said sec ond switch means and locking said switch means in these positions, means for energizing said relay means upon contact of said workpieces while said piece is held, normally open contact makingmeans for preparing a welding circuit by closing said conductor means. means for actuating said impact means to force said mechanical contact, and means including a timer for closing said contact making means prior to said mechanical contact.

2. Electric welding apparatus comprising alternating current supply means, capacitor means adapted to he charged from said supply means, normally closed switch means which upon open ing render said supply means ineffective, means for positioning two'work pieces to be joined relatively to each other in placeior welding but with one piece held at a distance from the other normally preventing direct contact therebetween, impact means for releasing said piece and for forcing said pieces into mechanical contact, conductor means for electrically connecting said pieces to respectiye terminals of said 0 nacitor means, energy consuming means connected in parallel to said capacitor means for discharge through a normally open switch means, relay means for retaining said switch .means in normal positions when tie-energized but energization opening said first switch means closing said second switch means and locking said switch means in these positions, relays means controllable from a point near said impact means for unlocking said relay means, means for energizing said relay means upon contact of said work pieces, while said piece is held, means for rendering said energizing means ineifective upon operation of said impact means, normally open contact making means controlled by said impact means and arranged in said conductor meansfor preparing a Welding circuit by closing said conductor means, and a power supply for actuating said impact means to establish said mechanical contact and an actuator operated by said power supplyand including a timer for closing said con,- tact making means prior to the mechanical contact.

Electric Welding app ra us com isin a guide casing; a plunger casing sliding on said guide casing, said plunger casing carrying percussion block and a work holderian d slidingly en,- gaging a working plunger adapted to impinge upon said block; means for supplying electric current to said block, said current supply means including a normally open switch and means for closing said switch shortly before said plunger impinges upon said block; a. source of working force tending to move said plunger towards said block when said casings are moved against each other; latching .means normally attaching said plunger to said plunger casing; and means associated with said guide casing for releasing said 13 latching means upon said relative movement of said casings.

4. Electric welding apparatus comprising a guide casing; a plunger casing sliding on said guide casing, said plunger casing carrying a percussion block and a Work holder, and slidingly engaging a working plunger adapted to impinge upon and to make electrical contact with said block; means for supplying electric current to said plunger; a source of working force tending to move said plunger towards said block when said casings are moved against each other; latching means normally attaching said plunger to said plunger casing; and means associated with said guide casing for releasing said latching means upon said relative movement of said casings.

5. Electric welding apparatus comprising a guide casing; a plunger casing sliding on said guide casing, said plunger casing carrying a percussion block and a piercing tool holder, and slidingly engaging a Working plunger adapted to impinge upon and to make electrical contact with said block; piercing means secured in said holder and including a working portion of non-welding material; means for supplying electric current to said plunger; a source of working force tending to move said plunger towards said block when said casings are moved against each other; latching means normally attaching said plunger to said plunger casing; and means associated with said guide casing for releasing said latching means upon said relative movement of said caslngs.

6. Electric welding apparatus comprising a guide casing; a plunger casing sliding on said guide casing, said plunger casing carrying slidingly fastened thereto a percussion block and holding means fastened thereto; a working plunger slidingly mounted on said plunger casing and adapted to impinge upon and to make electrical contact with said block; spring means tending to move said block towards said plunger, means for distancing said casings from a, work piece; means for supplying electric current to said plunger; a source of working force tending to move said plunger towards said block when said casings are moved against each other; latching means normally attaching said plunger to said plunger casing; and means associated with said guide casing for releasing said latching means upon said relative movement of said casings.

'7. Electric welding apparatus comprising a guide casing; a plunger casing sliding on said guide casing, said plunger casing carrying slidingly fastened thereto a percussion block and holding means fastened thereto; spring means tending to move said block and said holding means towards said guide casing; a working plunger slidingly mounted on said plunger casing and adapted to impinge upon and to make electrical contact with said block; spring means tending to move said block towards said plunger, means for distancing said casings from a work piece; means for supplying electric current to said plunger, normally substantially relaxed spring means tending to move said plunger towards said block when said casings are moved against each other; latching means normally engaging said plunger to said plunger casing; means associated with said guide casing for releasing said latching means upon said relative movement of said casings, and normally substantially relaxed spring means tending to move said plunger within said plunger casing for i e-engage ment by said latch means.

8. Electric Welding apparatus comprising a guide casing; a plunger casing sliding on said guide casing, said plunger casing carrying insulated therefrom and slidingly fastened thereto a percussion block; a work holder carried by said percussion block; a working plunger insulated from said guide casing, slidingly mounted on said plunger casing, and adapted to impinge upon said block; yielding switching means for making electrical contact between said plunger and said block before said plunger impinges on said block; spring means tending to move said block to wards said plunger; means fastened to said plunger casing for distancing it from a work piece; means for supplying electric current to said plunger; spring means tending to move said plunger towards said block when said casings are moved against each other; latching means normally engaging said plunger to said plunger casing; and means associated with said guide casing for releasing said latching means upon said relative movement of said casings.

9. Electric welding apparatus comprising a guide casing; a plunger casing of insulating material sliding on said guide casing, said plunger casing carrying insulated therefrom and slidingly fastened thereto a percussion block having a conical portion and fastened thereto a work holder; a Working plunger slidingl mounted on said plunger casing and adapted to impinge upon said block; longitudinally arranged spring means arranged for making electrical contact with said conical portion before said plunger impinges on said block; spring means tending to move said block and said work holder towards said plunger; means fastened to said plunger casing for distancing it from a work piece; means for supplying electric current to said guide casing and from there to said plunger; spring means tending to move said plunger towards said block when said casings are moved against each other; latching means normally engaging said plunger to said plunger casing; and means associated with said guide casing for releasing said latching means upon said relative movement of said casings.

10. Electric Welding apparatus comprising a guide casing; a plunger casing sliding on said guide casing, said plunger casing carrying insulated therefrom and slidingly fastened thereto a percussion block and fastened thereto a work holder; a conductive sleeve mounted within and insulated from said plunger casing; a working plunger slidingly mounted within said sleeve and adapted to impinge upon said block; means for making electrical contact between said plunger and said block before said plunger impinges upon said block; spring means tending to move said block towards said plunger; means fastened to said plunger casing for distancing it from a work piece; means for supplying electric current to said sleeve and hence to said plunger; spring means tending to move said plunger towards said block when said casings are moved against each other; latching means normally engaging said plunger to said plunger casing; and means associated with said guide casing for releasing said latching means upon said relative movement of said casings.

11. Electric welding apparatus comprising a guide casing; a plunger casing sliding on said guide casing; insulating means lining said plunger casing; a metallic percussion block slidingly arranged within said insulating means; a

work holder fastened to said percussion block; a conductive sleeve mounted ithin said insulating means; a metallic workin plunger slidingly mounted within said conductive sleeve and d ted to im i g upo a d b k; mean ior electrically contacting said plunger with said block; means for supplying electric current to said conductive sleeve and h nce to said plunger; means tending to move said plunger towards said block when said casings are moved against each other; means normally engaging said plunger to said plunger casing; and means associated.v with said guide casing for releasing said engaging means upon said relative movement of said case ings.

12. Electric welding apparatus comprising a metallic guide casing; a metallic plunger casing sliding on said guide casing; insulating means lining said plunger casing a metallic percussion block slidingly arranged Within said insulating means; a work holder fastened to said per.- cussion block; a conductive sleeve mounted within said insulating means; a metallic working plunger slidingly mounted within said conductive sleeve and adapted to impinge upon said block; longitudinally arranged spring means arranged for making electrical contact with said plunger and said block before said plunger impinges upon said block; spring means tending to move said block towards said plunger; means fastened to said plunger casing for distancing it from a work piece; means for supplying electric current to said metallic sleeve and hence to said plunger; spring means tending to move said plunger towards said block when said casings are moved against each other; latching means normally engaging said plunger to said plunger casing; and means associated with said guide casing for releasing said latching means upon said relative movement of said casings.

1 Electric welding apparatus comprising a guide casing; a plunger casing sliding on said guide casing; insulating means lining said plunger casing; a conductive sleeve mounted sion block slidingly arranged within said conductive sleeve; a work holder fastened to said percussion block; a Working plunger slidingly mounted within said insulating means and adapted to impinge upon said block; means for electrically connecting said conductive sleeveand said percussion block to said plunger and said block; terminal means mounted. on. said punger casing for supplying electric. current to said conductive sleeve and hence to said block; means tending to move said plunger towards said block when said casings are moved against each other; means normally engaging said plunger to sa d plunger casing; and means associated wit v said guide casing for releasing said engaging means upon said relative movement of said casings.

14. Electric welding apparatus comprising a guide casing; a plunger casing sliding on said guide casing; insulating means lining said plungwithin said insulating means; a metallic percuser casing; a metallic percussion block slidingly arranged within said insulating means;- means for normally retaining said percussion block in withdrawn position; a work holder fastened to said percussion block; a conductive sleeve mounted within said insulating means; a metallic working plunger sIidi-ngly mounted within said conductive sleeve and adapted to impinge upon block to move it forward from said withdrawn position; means for electrically contacting said plunger with said block; main terminal means mounted on o o sa d asin s su p n electric current to said conductive sleeve and hence to said un er; mean nd ng to. move di uns t ard aid b o k w en sa d asings are moved against each other; means normally engaging said plunger to said plunger casing; auxiliary terminal means mounted on said plunger casing; and means for making electrical contact between said work holder and said auxiliary terminal means when said ork holder is in said withdrawn position; and means associated with said guide casing for releasing saidengaging means upon said relative movement of said casi s o cause im ngem o said un er upon said block and forward movement of said block and said work holder.

15. Electric welding apparatus comprising .a metallic guide casing; a metallic plunger casing sliding on said guide casing; insulating means lining said plunger casing; ,a metallic percussion block slidingly arranged within said insulating means; a work holder fastened to said percussion block; a conductive sleeve mounted within said insulating means; a metallic working plunger slidingly mounted within said conductive sleeve and adapted to impinge upon said block; means for electrically contacting said plunger with said block before said plunger impinges upon said block; timing means for adjustably retarding the relative movement of said plunger and said block; spring means tending to move said block towards said plunger; means fastened to said plunger casing for distancing it from a work piece; means tending to move said plunger towards said block when said casings are moved against each other; means normally engaging said plunger to said plunger casing; and means associated with said guide casing for releasing said engaging means upon a predetermined relative movement. of said casings.

l6. Electric weld-ing apparatus comprising ametallic guide casing; a, metallic plunger casing. sliding on said guide casing; insulating means lineing said plunger casing; a metallic percussion block slidingly arranged within said insulating means; a work holder fastened to said percusgn bl ck; a c ndu t ve sle v mounted Within. aid i u tin m ans; a m tallic W rkin -plung er slid ne moun d with said onductive sleeve a d ada ted to mpi e u on sai b ock; ns fo lec r ca y co a t n aid plu e with said block before said plunger impinges upon a o k; sp mean end to ove a d blook towards said plunger; means fastened to said plunger casin for distancing it from a-work piece; means tending to move said plunger to. wards said block when said casings are moved against each other; means normally engaging said plunger to said plunger casing; actuatingmeans associated with said guide casing for re-. leasing said engaging means upon relative move, ment of said casings; and means for adjusting said actuating means to release said engaging means when said casings have reached a prede: termined relative position.

17. Electric welding apparatus comprising electric energy supply means, a gun havin a chuck ior holding one of two work pieces relatively to the other and impact means for forcing said pieces together by applying a blow to said chuck, conductor means for electrically connecting said pieces to respective terminals of said supply m an W DQIm Y se at d con acts ar an ed 76 in series connection in said conductor means for 17 preparing, when closed, a welding circuit, one contact being carried by said impact means and the other by said chuck, and means for releasin said impact means to close said contact prior to the application of said blow by said impact means.

HAROLD J. GRAHAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 17,949 Chubb Feb. 3, 1941 1,066,468 Chubb July 8, 1913 1,269,726 Mershon June 18, 1918 Number Number 15 520,411

Name Date Apple Feb. 24, 1920 Phelps Sept. 11, 1928 Siebs et a1 Nov. 24, 1931 Pfaustiehl June 25, 1935 Cummins Sept. 15, 1936 Knowles et a1 June 29, 1937 Gade Sept. 3, 1940 Somars Sept. 4, 1945 Nelson June 25, 1946 Weinhardt et a1. Apr. 29, 1947 FOREIGN PATENTS Country Date Great Britain Apr. 23, 1940 

